Project Summary Hepatocellular carcinoma (HCC) is the fifth most common cancer and the second leading cause of cancer- related death in men worldwide. A unique feature of HCCs is that they undergo intra-hepatic metastasis, causing aggressive progression that does not respond to therapy. The incidences of HCC are on the rise in the US. Clearly, a better understanding of the mechanisms underlying progression and resistance of HCC will be important in designing efficacious therapeutic approaches. The current proposal focuses on the forkhead box transcription factor FoxM1, which is centrally important for HCC progression. FoxM1 over-expression is a marker for aggressive HCC and poor prognosis. In experimental models, FoxM1 is essential for HCC development and progression. Mice lacking FoxM1 expression in the liver fail to develop HCC. Moreover, we developed a bi-transgenic strain (FoxM1bTg;Arf-/-) expressing FoxM1 in the absence of its inhibitor, the tumor suppressor ARF, when subjected to a tumor promotion protocol develops metastatic HCC. This bi-transgenic strain offers a rare model to study progression and metastasis of HCC. Recent studies provided evidence for liver cancer stem cells (LCSCs) in HCC. Their presence is associated with increased tumorigenicity, recurrence, chemoresistance, and poor survival. In this proposal, we will seek in vivo evidence for a role of FoxM1 in the survival of the LCSCs, and investigate the mechanisms by which FoxM1 support their survival and proliferation. We will test a novel hypothesis that activated Akt and FoxM1 collaborate to drive metastasis of HCC. Also, we will use our bi-transgenic mouse model to investigate effects of small molecule Akt-inhibitor on HCC metastasis. We provided genetic evidence that the tumor suppressor ARF inhibits FoxM1-induced metastasis of HCC, and characterized a 19-aa peptide derived from mouse ARF that is sufficient to inhibit FoxM1. We will test the hypothesis that the ARF-peptide, by eliminating the LCSCs, increases recurrence-free survival. Also, we will determine whether the ARF-peptide sensitizes HCC to sorafenib. The aims are: 1. Investigate the mechanisms by which FoxM1 supports the liver cancer stem cells. 2. Determine the mechanism by which FoxM1 activates Akt and investigate whether activated Akt collaborates with FoxM1 to drive aggressive HCC progression. 3. Investigate the effects of the ARF-derived peptide inhibitor of FoxM1 on the LCSCs and on recurrence-free survival. The available therapies do not work for aggressive HCC. There is evidence that inhibition of FoxM1 blocks aggressive HCC progression. Clearly, a deeper understanding of the FoxM1-pathways that define its role in HCC progression will aid in developing new therapeutic approaches that are effective in treating the disease. ! !